Physiological Regulation Mechanism Of Exogenous Brassinolide On Seed Germination And Growth Characteristics Of Rice Under High Temperature Stress

In this experiment,’Xiangwanxian 13’was used as the material,and different concentrations of exogenous brassinolide were used to soak the seeds to explore the effects of different temperatures on the germination characteristics of rice seeds,and to determine the germination rate,antioxidant enzyme activity,andmalondialdehyde content,alpha amylase activity,soluble sugar,H₂O₂ content and other indicators,and transcriptomics analysis,to explore the regulation mechanism of rice seed germination under high temperature stress,and provide the application of brassinolide in rice production practice theoretical basis.The main results of this study are as follows:Seed soaking with suitable concentration of exogenous brassinolide can alleviate the damage caused by high temperature to seed germination to a certain extent,and the effect of soaking the seeds with 0.05μmol/L exogenous brassinolide is the most obvious,which can be significant It can promote the growth of rice radicle under high temperature stress,increase root fresh weight,bud fresh weight,bud dry weight,etc.,and can significantly increase the SOD activity of rice seeds under high temperature stress,reduce MDA content,and increase soluble protein content.（2）After soaking the seeds with 0.05μmol/L exogenous brassinolide,it can significantly increase the activity of SOD,POD,CAT,soluble protein content,andα-amylase in the seeds（SG3）whose endosperm is about to rupture during the germination of rice seeds under high temperature stress.Compared with the control,the content of active and soluble sugars were increased by 1.73%,129.81%,13.06%,21.53%,97.74%,and87.70%respectively.At the same time,its MDA content and H₂O₂ content were reduced by31.05%and 11.88%compared with the control.Through hormone determination,it was found that after 0.05μmol/L exogenous brassinolide soaked rice seeds under high temperature stress,the IAA and GA content of seeds（SG3）whose endosperm was about to rupture during the germination process were significantly reduced compared with the control.（3）Through transcriptomics analysis,it was found that under high temperature stress,the endosperm seeds（SG3）that are about to rupture during the germination of rice seeds after the 0.05μmol/L exogenous brassinolide soaking treatment had a total of 6681differential genes,of which 2873 were Genes were significantly up-regulated,and 3745genes were significantly down-regulated.After high temperature stress,5528 differential genes were enriched into 52 categories,of which 26 belonged to biological processes,14belonged to cellular components,and 12 belonged to molecular functions.Through KEGG pathway analysis of differential genes,it is found that five pathways are significantly enriched,namely metabolic pathways,biosynthesis of secondary metabolites,biosynthesis of antibiotics,microbial metabolism in different environments,and biosynthesis of phenylpropane.Through the q PCR verification of the differential genes related to the phenylpropane biosynthetic pathway of rice seed germination under high temperature stress,it was found that the change trend of the selected differential genes was consistent with the transcriptome sequencing results（FPKM）,indicating that the 0.05μmol/L exogenous brassinolide soaked seeds The treatment can alleviate the effect of high temperature on the germination of rice seeds by regulating the related genes of the phenylpropane biosynthesis pathway.